A type of bacteria that commonly infects infants is responsible for causing stomach ulcers in adults. Now researchers are learning that this same bug may keep women from getting MS.

Australian researchers have discovered that a type of bacteria called Helicobacter pylori (H. pylori), which causes stomach ulcers, may also protect women from developing multiple sclerosis (MS). Women with MS were found to have fewer immune system cells called antibodies in their blood designed to fight H. pylori. This suggests a possible link between too few H. pylori bacteria and the development of MS.

Professor Allan G. Kermode of the Centre for Neuromuscular and Neurological Disorders at the Western Australian Neuroscience Research Institute and colleagues recently published their results in the Journal of Neurology, Neurosurgery, and Psychiatry. For their study, 550 people with MS were matched by gender and birth year to 299 health volunteers. Blood samples from all of the participants were exposed to an enzyme that binds to antibodies that fight H. pylori. Antibodies in a person’s blood indicate that they’ve had past exposure to a particular bacterium.

Antibodies are the immune system’s way of remembering an infection and making us immune to it in the future. That’s why vaccinations work to prevent disease: tiny amounts of the actual infectious agent are introduced in order to prompt the immune system to make protective antibodies. The antibodies will prevent a serious reaction during a real-life exposure later on.

Only 14 percent of the study’s female volunteers with MS tested positive for H. pylori antibodies, compared to 22 percent of their healthy peers. This suggests a connection between MS and H. pylori, but it’s too soon to draw any cause-and-effect conclusions.

Moreover, in the women with MS who tested positive for these antibodies, the more antibodies they had, the less severe their disease course appeared to be. This indicates that the antibodies may play some role in regulating the immune system.

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Curiously, the study’s male participants with MS didn’t match the females when it came to H. pylori. The antibody levels in the men with MS were no different from that of their matches in the control group.

H. pylori and the ‘Hygiene Hypothesis’

A common bacterium that is thought to be spread from one person’s mouth to another, the “helico” part of the Helicobacter pylori name refers to its spiral shape — like helicopter blades. Children are thought to be most at risk for H. pyloriinfection because they haven’t yet learned to practice good hygiene.

“H. pylori is usually acquired in infancy from family members,” explained Kermode in an interview with Healthline.

When the bacteria take up residence in the stomach, most people are able to fight them off without incident. But for some people, the invader can wreak havoc, causing damage to the mucus lining of the stomach resulting in painful ulcers.